Friday, December 12, 2008

I hear all the time that religion doesn't make people mistrustful of science all the time. It just happens that there's a direct correlation between religious belief and the ignorant criticism of evolution. It's not all science. Just that one area.

In 1859, a solar flare so powerful occurred that it shorted out telegraph wires causing fires on the desks of the operators in the US and Europe. In addition, it reduced the amount of atmospheric ozone by about 5% (Note to global warming deniers: This would only be a short term effect and human made ozone depletion is long term since CFCs don't readily leave the atmosphere).

Thursday, November 20, 2008

New Scientist has an article up describing an attempt to meld science and Hollywood. Initially I liked the idea. How could I really be against getting better science into mainstream media?!

And then I remembered: The majority of science is mundane, boring, tedious number crunching. It's not exciting. It doesn't fit in Hollywood. It's like putting a round peg in a square hole. So what can be done to try to make the science exciting enough for Hollywood?

As I see it, there's two options:

1) Skip all the boring bits and get straight to the "Whiz Bang" bits and "Eureka" moments.

My problem with this is that either way, it's still misportraying science. The article gives a perfect example:

[MacFarlane] just finished making a Family Guy episode based on the possibility that there are multiple universes, prompted by a documentary he saw on the subject.

"I didn't really know that that was a real thing, that it was possible [and] being theorised about," he said. "So we did a story about it."

What's wrong with this? Where's the good science in multiple universe hypotheses? Where's the testing? Sure multiple universes sound good and sciencey, but when you get right down to it, it's not. It's a possible branch of science that's still in its infancy. It is a nice construct to start working from, and then develop ways to test it as we go, but chances are, like so many other things, it's quite likely that if/when we ever do test it, it will turn out to be bogus. And do we really want to be showing the public more bits of tenuous science that in all honesty, are pretty hollow?

While I see Hollywood's reasoning for doing it (it draws in the geeks), I also see the problem: It continues to confuse the picture of what science really is. We already have folks like the Discovery Institute hard at work doing that.

So while I appreciate the attempt from MacFarlane and Hollywood to put a bit more scientific rigor into their work, I just don't think it will work out too well for the simple reason that the two have very different intentions: One seeks to entertain, the other seeks to discover.

Meanwhile, I do like what the Zuckers said in the article about how science saved their daughter's life:

"They gave here a shot of insulin and this was like a miracle, because she was laying there on the examining table, and within a few hours she came alive again, her lustre came back," Janet Zucker said.

Religulous has been out for a good while now, but I finally got around to seeing it last night. My overall impression of the movie wasn't overly impressed.

That being said, I think a good subtitle for this movie would be "Bill Maher preaches to the choir."

The large majority of this movie is going around to various religious people and showing that they (a) believe in things that are completely nuts like the virgin birth, or (b) are stunningly ignorant about their own religious history.

The reason that I say Billy is preaching to the choir is that it isn't likely that anyone that is religious sees anything wrong with this. They either see bogus miracles as truly miraculous, or are equally ignorant. As such, anyone that doesn't already agree with what Bill is saying probably won't get it.

And Maher doesn't even seem to care. Instead of trying to explain just why these people are ignorant, and trying to actually teach the audience something about what he's talking about, he just tosses things out there with no explanation. A perfect example is when Bill is talking to a Muslim about the view of many Muslims that anyone who challenges their religion should be killed. The Muslim says this isn't true and that it allows for discussion. Maher brings up the case of Salman Rushdie, and asks whether or not he deserves to be killed. The Muslim tries to waffle his way out and gives a non-answer worthy of the Discovery Institute.

I know who Salman Rushdie is. Maher knows who Salman Rushdie is. The Muslim Bill is talking to knows who Salman Rushdie is. But does the audience? Not exactly likely. I only know because SOMA brought him to KU a few years back. But Maher doesn't even try to take a bit of time to explain the situation. If you already know, then it makes sense. If you're not part of the choir, well, that part's probably lost on you.

Maher also seemed to use quite a few silly tricks when interviewing people. He'd ask a serious question and inevitably, the religious person would have to stop because they couldn't answer it. Of course, the way the editing was done, it makes me genuinely curious as to how many of the dazed pauses were legitimate and how many were edited in. I'd like to give the benefit of the doubt here, but some just looked staged.

Another trick Maher used to force people to slip up was to ask a legitimate question and then, when they tried to answer it, make a joke out of it. The natural response to this is to stop and wonder, "How do I respond to this? As a serious question, or to the joke?" Those forced pauses I'm sure were abused as well.

Maher also tended to go after some people with pathetically weak education and theology. Showing up to a trucker's church? Yeah. Insightful theology there Billy.

There were some highlights of Bill meeting with some better religious authorities. As usual, former head of the Vatican Observatory, Geroge Coyne impressed me with his honest and informed answers. Francis Collins, head of the Human Genome Project, was better than most but still made himself look like a twit without Maher even having to try. But perhaps my favorite person Maher talked to was a Catholic priest just after Maher got kicked out of the Vatican. This guy admitted that most of the religion was full of hot air and was extremely laid back about the whole deal. Why can't we get priests like him in the US?!

So overall, the show had its high points and low points. It was 90% Bill showing that religious people are, by and large, at least compartmentally stupid. But as I said before, to those that would see this as such are people that would already agree. Those that can't see this are the ones being made fun of.

But what about that other 10%?

This last little bit was what I think the real highlight of the movie was. It was mentioned right at the beginning, and then was the main point at the end. One quote summed it up pretty well. I know this isn't quite right, but the notion is, "It's a shame that humanity developed the ability to destroy the world before it developed the ability to be rational."

This is the point that I agree with wholeheartedly. For the first time in human history, we have the ability to destroy our entire species. With this horrible threat, we can no longer practice the naive rituals of non-thought, however comforting they may be.

I really wish this theme would have been worked far more throughout the film, and stronger connections drawn with the lack of critical thinking and the consequences its already wrought. Instead, Maher left the cause and the effect only connected with a tenuous slippery slope. I think the message is solid, but this movie did not do a good job of showing it. The only thing it did do, was provide a bit of schadenfreude for those of us that already get it.

Tuesday, November 18, 2008

Sometimes, after I really haven't dealt with any Creationists in a good while, I start to forget just how intellectually bankrupt they are. I start to think that, maybe they really do care about things like evidence and that they're just confused about it or blissfully ignorant.

Or maybe they do want to use the scientific method, but just can't quite remember what it was because junior high was really just that long ago and they're much too busy studying the Bible to have time to brush up on even the basics of that which they criticize.

Or just maybe they try not to use logical fallacies, but can't quite get a grasp on what things like circular logic, equivocation, strawmen, and the like are.

And then I see a bumper sticker like this one.

And suddenly I remember; Creationists don't care about evidence; Creationists don't care about science; Creationists don't care about logic. They're just that dense.

Tuesday, November 11, 2008

Last week I said one of the reasons I haven't been posting much is that there just hasn't been much going on besides politics and we're all sick to death of that. Another reason is that, now that I've graduated, I've been able to devote more time to other hobbies that aren't things I typically post about on this blog. I don't intend to make them a major portion of my blog, but it's worth mentioning.

In particular, I've gone and gotten myself a Netflix account. I've seen a few films I just missed in theaters that I wanted to catch (like the Simpsons movie), a few that are classics I've wanted to see for a long time (Seven Samurai) and quite a bit of anime (Full Metal Alchemist, Hellsing and Cowboy Bebop). Most of my evenings are spent, at least in part watching something from Netflix.

I've also been playing a lot of World of Warcraft. With the new expansion coming out this week, it's been more fun because many of the players that disappeared over the summer in my guild are coming back, so raids have been much more frequent and well attended.

For those that are interested, I have three characters I play regularly. All are on the Stormreaver. My main is Tiadara. She's my badass shadow priest. She enjoys short runs through Karazhan and playing mana battery for 24 other guys. Hot.

My second 70 is Ellobrosa. I don't tend to play him much anymore since Huntards are a dime a dozen so his main purpose is to help use his Track Humanoids skill to find those annoying Horde that just ganked my lowbies or guild mates.

Sebiole is my third character I play regularly. I got tired of not being able to find a tank so I'm leveling her prot spec. Not a terribly good idea. Sure, I have tons of health and don't die easily, but damn does it take forever for me to kill stuff.

So that's the digital persons I hide behind most nights I'm not out being social.

Aside from WoW, I've also been able to take more time to head to conventions. And by conventions, I mean convention. Sadly, there's very few in the midwest worth visiting. I did manage to make it to Archon 32 last month. It was pretty lame aside from the costume contest, but since costuming is what I go for anyway, I didn't mind. My gallery of pictures of the costumes is here.

I'll be at Nebraskon this coming weekend. It's looking like I'll be there as one of the official representatives of Naka Kon which is the Kansas City anime convention originally started by KU's anime club. I've been made a staff member of that so show up if you're in the area! I'll be running a panel entitled "The Science of Anime" which will attempt to answer questions like, "If someone were really falling the amount of time it took Naruto to shout that ridiculously long sentence, how far would he have fallen and how fast would he hit the ground?" It should be fun.

Back when I was still attending MSU, I attended a regional meeting of of the Society of Physics Students (SPS). One of the topics was the number of females in STEM (Science, Technology, Engineering, and Mathematics) fields. The speaker challenged us to try to name famous women that had made notable contributions to our fields.

I listed those few I could come up with, but in the entire auditorium, I was the only student that could name a single one.

In a similar situation, while I was taking Calculus 2, my professor said that if the entire class could name three female mathematicians, he would cancel the final. All the students began flipping furiously through their textbooks for names, but only turned up one.

For anyone in the field, it's obvious that females are grossly underrepresented (astronomy seems to be one of the hottest scientific fields for women however), but the question has always been, "why?".

A recent paper from the AMS has taken a fresh look at this issue. What the paper describes is likely not surprising to most people; The most significant factors the researchers found was cultural views on such fields. In countries which do not afford women the same opportunities as males for mathematics education, women obviously are strongly underrepresented. However, when the ability is given to compete equally as with Title IX in the US, women become more frequent in the fields. Yet still not as represented.

Part of the reason, the researchers conclude, is that there remains some social taboo against such fields. Women from Asian and Indian countries are far more common in the STEM fields.

Another interesting note was that even in societies were math is seen as "geeky" and not an appropriate field for women, girls tend to do just as well as males in elementary schools. Only when social pressures start taking over in middle schools do girls start falling behind notably.

So how does the US stack up here? As you might expect with how poor I and other science bloggers have noted the US education system is in respect to science, it doesn't do too well:

Asian girls and white girls who are immigrants from Eastern Europe are well represented among the very top students identified in the extremely difficult mathematics competitions discussed here; it is only USA-born white and historically underrepresented minority girls who are underrepresented, underrepresented by almost two orders-of magnitude relative to Asian girls educated in the same school systems

Wednesday, November 05, 2008

If everyone's been wondering where I've been the past few months, I've been taking a break from blogging. The election stole the spotlight from everything else, so there really hasn't been much to write on. The creationists have been shoved out of the spotlight. Astronomy news doesn't come as frequently anymore since I'm not constantly reading journals after graduation. So there really hasn't been much to say. And if there is, that crazy bald guy seems to always beat me to it.

But now all the political nonsense is out of the way, I'll try to post a bit more frequently.

Or if you want to be lazy and listen instead of reading, you can always pick up a podcast. Fortunately, the newest one is available from sky at night (warning, MP3 link. Click to stream. Right-Click > Save as to download).

Since my lease on my apartment is about to expire here, I've been concerned with how I'm going to get my junk a few miles down the road. What a trifling concern that is compared to getting it to even a new civilization even as close as the moon. Fortunately, at Colony Worlds, we hear about a Romanian team is looking to make small package delivery to the moon possible. I think I'll be sticking to U-haul for me though.

Wednesday, July 09, 2008

In reality, this isn't surprising. It's not a matter of, "the virtual world ... winning." I strongly suspect that about the same number of kids could also identify Paris Hilton, and other people that aren't at all important in their lives. We're programmed to remember people (or in this case anthropomorphized aliens) much better than mundane objects.

But we'll just let the biologists have their good cry over it. There there. We still love you even if you can't defeat a Dark Lord of the Sith.

All over the world, psychics, spiritualists, and other cons claiming to have supernatural powers get away with taking in the gullible. But it looks like Russia has put a stop to at least one of them. The story tells that Grigory Grabovoy scammed people into thinking that he could raise the dead if they just paid him enough money (the equivalent of a few thousand dollars).

He gets 11 years in prison for his scam.

Obviously his lawyers don't think it's fair, saying, "We think the sentence is based on speculation and is absolutely unfair."

Speculation? Someone taking money for services that I damn well bet he hasn't performed is speculation? ROFL!

Tuesday, July 08, 2008

I haven't been working on the research I started last semester this summer (although I intend to get back to it when I really get settled with everything else going on). However, there's other groups out there working on the same issue.

One of the predictions that the original paper we were basing our work off of said that, if planets could induce massive flares, we should see enhanced X-ray activity on stars with close in planets.

This isn't a 100% sign that the planets could induce as massive of flares as the ones we're interested in, but it's one of the necessary conditions that had better be confirmed.

So this group at Harvard took a look at the amount of X-rays coming from 230 stars. And what did they find?

invariably the close-in samples have X-ray luminosities higher than that of the distant sample.

Horay! Prediction verified! Right?

Well, not just yet. Like all good scientists, these guys looked at possible sources or error and bias. And the word on that one?

observational biases account for about half of the observed differences seen in the data.

Eep! Ok. But if half the data isn't helpful, is the other half still good enough?

Yep. And what's more, after some modeling, they found that the enhancement may be be dependent on the simple multiple of the fields (the planet's and the star's). Thus, if we know the magnetic field of the star, we may be able to start probing the magnetic fields of planets for the first time.

Monday, July 07, 2008

I did my best to provide some pictures to illustrate what I was talking about, but they weren't anything exciting. What would be really exciting is if you could see this for something really cool. Like a Hubble image.

Turns out, you can! PBS put together a wonderful little flash on how the amazing Hubble images are made. It's the exact same as what I talked about (plus the image aligning since you have to combine images) but in a much flashier format.

I know I’m behind the curve here, but now that I’ve graduated, I’ve got a lot more free time to read books, watch movies, play games, talk to friends and all that jazz.

One of the things that I’ve only just now gotten around to is watching Jesus Camp. I knew it was scary just how crazy these people were, so for the most part, it wasn’t surprising, but I figured I’d share my thoughts on it anyway.

In the very first scene, we see the leader of the camp, Becky Fisher, screaming at kids about how, if God can do anything, then he should be able to fix “this sick ‘ole world”. Hahahaha. Sure. Just pray. Yeah…. Shame prayer doesn’t work. This is again demonstrated later when Rachael (another girl in the camp) prays to get a strike while bowling. She rolls a gutter ball.

She then tells kids that, “We have too many Christian grown ups who are fat and lazy.” Sure. And she’s one of them. She’s by far the fattest one in the entire film and is later seen teasing her hair. Yeah. That’s getting something done… Shame she can’t get these kids to do something productive instead of harassing people with nonsense.

Next, she leads the group in prayer in tongues. Now, back in high school, I did a bunch of theater. One of the things that we had to learn was how to quickly speak gibberish and make it convincing enough to actually sound like a language. It’s not that difficult, but it takes some practice. When you’re good at it, it rolls right off your tongue and sounds pretty good to someone who doesn’t know you’re not actually speaking gibberish. The thing that amazed me about this is that these people aren’t even good at it! Their gibberish is running through a few mushed up syllables. And they really thing it means something! The adults were obviously better than the kids, but having a lifetime of practice, they’d better be.

The film then shows the camp leader watching the video of these kids and saying, “she’s not out of it. She’s very aware of what’s going on.” Well yeah. You know what’s going on, but that doesn’t mean it has to make sense or have some profound meaning. And it certainly doesn’t mean that they’re “hooking up with the Spirit.”

Becky brags about being able to go onto a playground and tell kids about God and get them to see “visions”. Well duh. Kids are imaginative and open to suggestion. Why do you think that psychologists are required to undergo training before they ask kids about experiences? They have to make sure they don’t lead the kids inadvertently. There’s numerous cases out there (many times involving ignorant church officials) in which people asking them questions have led kids to believe that they were sexually abused, leading to emotional trauma when in fact, no such thing had occurred. What Becky does is probably less harmful, but is no more meaningful than this. The fact that she brags about it is just disgusting.

She talks about suicide bomber camps training kids and says that it’s great that they can get kids so dedicated. She says, “I want to see young people who are as dedicated to the cause of Jesus Christ as the young people are to the cause of Islam. I want to see them radically laying down their lives for the Gospel…”

Wow.

Next up we see one of the kids, Levi, watching a Creationist propaganda video. It’s got the normal lies about what science actually says (“Did we come from an explosion? Are you a gob of goo?”). The mother then starts talking about Global Warming, teaching her son to dismiss it because it’s “only gone up 0.6º.” Talk about a lack of understanding of the issue. Levi then says he, “feels Galileo made the right choice by giving up science for faith.”

Another family does the Pledge of Allegiance. Except it’s not even the one to the US. And these people claim that we’re the ones trying to subvert the pledge? LOL!

At the camp, Becky stars off with a brain numbing sermon about how sin is like a baby tiger, that if you feed it, it gets big and eats you. Then right in the middle of it, she goes on a crazy rant about how evil Harry Potter is, how he’s an “enemy of God”, and how if he was in the OT, he’d be “put to death.” What a sweet message.

She then does the magic trick of the guilt trip, trying to make people feel bad for being humans because they’re not Christian enough. And you “can’t have phonies in the army of God.” “You know what need to repent of.” Sounds more like an interrogation technique than anything else. Especially when some of the kids antagonize another for looking like Harry Potter and another for having seen it at his father’s house.

One of the male leaders of the camp gets testy about ghost stories because they, “don’t honor God.”

Rachael has a segment about “dead churches” in which she says that God likes churches in where people are jumping up and down and being overly excited. Funny. If I was invited to a party in my honor, I’d prefer people not act like complete idiots. At least not till I’ve had a few drinks too…

In another scene, Levi is practicing a sermon he’s going to be giving about how he feels that his generation is a key generation for blah blah blah blah…. He then says that he’s not the one that writes it, but that it’s God writing it. Hmmm… no. I think it’s the pastors that said the exact same thing earlier that you’re cribbing from. I guess citing your sources is optional for these guys.

Later on, there’s more trivial examples of doing nothing while thinking they’re doing something by smashing cups with hammers. There’s a lot of crying about it too.

The trip to Haggert’s New Life Church is especially ironic given his recent stumble.

In the end, Becky gets on a radio show and outright admits that she is quite happy to indoctrinate children and that democracy is bad. She’s just scary. And giving her access to children is worse.

Sunday, July 06, 2008

IT'S an embarrassing gap in astronomers' knowledge. Despite relying on type Ia supernovae as tools to measure the dark energy speeding up the universe's expansion, they still don't know exactly what causes the blasts. Now the picture has got even fuzzier.

Ugh. This is why I can't stand most science journalism. It takes what's a pretty cool journal article about people figuring out how our universe works and refining our knowledge, and acts like they're a bunch of bumbling morons.

*headdesk*

If you didn't follow the link to read the rest of the article, it basically says that a new paper is challenging the long held idea that type Ia supernovae come from white dwarfs pushed over their Chandrasekhar limit (the mass limit for a core before it explodes as a supernova) by mass being dumped on them from a companion star.

The evidence thus far seems to fit pretty well. There's not much hydrogen in the spectra, so we know these supernovae aren't normal stars, still surrounded by their hydrogen atmosphere. The total amount of energy fits well. The shape of the light curve works. We see them in old galaxies which should have lots of white dwarfs.

But the issue now is that recent studies have been indicating that we're seeing them in places with lots of active star formation too. In fact, it's being suggested there's even a correlation between the number of Ia supernovae and the amount of star formation. If that's the case, then this suggests that, at the very least, old dead cores can't be the only way to form Ia supernova.

So what's the "new" explanation? The paper doesn't say. There's a hint at the end effectively saying "stay tuned for paper #2!" but no word on what it's going to say yet.

But what does this all have to do with the part of the article I quoted earlier about the age of the universe?

Absolutely nothing!

Regardless of whether or not we know exactly what's causing these supernovae, we still know they're excellent standard candles because we can check them against other distance measuring methods (such as the P-L relation of Cepheids or the Tully-Fisher relation). It doesn't matter if it's an overburdened white dwarf or God letting off cosmic farts. Either way, we've observed that they all have an absolute magnitude of -19.3.

Not knowing exactly what causes type Ia supernovae doesn't change the fact that we know how bright they are! Since that doesn't change it doesn't make any difference on our understanding of the age and size of the universe! Tossing in that gibberish about the size and age of the universe is a complete non-sequitor.Pritchet, C., Howell, D., & Sullivan, M. (2008). The Progenitors of Type Ia Supernovae The Astrophysical Journal, 683 (1) DOI: 10.1086/591314

Thursday, June 26, 2008

Two years ago, I first got into the show Battlestar Galactica. Since then, I've been a gigantic fan (who knew I'd get into a show created by Mormons). The episode a few weeks back was, well, a cliffhanger to put it mildly. Unlike most episodes, it didn't end with the typical "stay tuned for a sneak peek at next week's episode" and hinted that BSG wouldn't be on for a bit.

Oh well. I suppose that will give the rest of you a chance to catch up.For those that don't understand the term "frack", it's the term that characters use in the show as a substitution for the obvious swear word. And yes, it has worked it's way into my everyday language.

Monday, June 16, 2008

Thursday, June 12, 2008

I’m not entirely sure why, but recently, in various forums I hang out on, I’ve been seeing a particular creationist argument pop up that’s fairly annoying. The argument is that the universe can’t be as old as astronomers say it is because, if it were, the spiral arms in galaxies would “wind up”.

This argument is pretty convincing at first, because it plays on the expectation that galaxies are fairly straightforward systems without dirty little tricks up their sleeves. If this were the case, galaxies would behave like the solar system wherein the things towards the center go around quickly and objects towards the edges slowly work their way around. Thus, if you started everything on a straight line, the inner part would have orbited several times while the outer edges would barely have budged thanks to the fact that those inner bits not only move faster, but have a shorter distance to travel in their smaller orbits.

Expectation wise, galaxies shouldn’t have graceful arms that tend to only go about half a full turn. Unless, of course, those expectations are wrong. And I’m sure by now most readers are anticipating what should be the obvious answer: They are.

The first thing that’s wrong is that galaxies don’t behave like our solar system. This was first realized in 1959 in the galaxy M33 by Louise Volders. In the 1970’s, this non-Keplarian motion was discovered in more and more galaxies by Vera Rubin, which is one of the foundations for the need for Dark Matter. Instead of velocities trailing off in an exponential decay like we see in the solar system, most galaxies tend to have fairly flat velocity curves as shown in the figure. A flat rotation curve means that galaxies don’t wind up and if they do, it would be very slowly.

Of course, this raises an even more interesting question. Even though we’ve established that these arms could be very old, it still doesn’t say anything about why you have regions in the galaxy where they exist in the first place. What’s so special about spiral structure!?

The answer to this question is profound because it gets to the very nature of what spiral arms are and, as with before, it’s something that completely defies what you’re probably thinking if you’re not already familiar with this topic: Spiral structure is the result of spiral density waves...

Whatever the hell that means.

Unfortunately, there’s no real good way I’ve yet come across to explain this. Silly analogies with traffic jams tell you what is going on, but says nothing of why it happens. And that “why” is fairly important, lest we be accused of making up just-so stories.

I’m going to skip the math since it requires a course in mechanics and quite a bit of calculus to go through and I’ll just get to the heart of what it reveals.

Let’s start off with an idealized galaxy in which we have everything as simple as we can get it. Let’s pretend the galaxy is a perfectly uniform distribution of gas and dust in perfectly circular orbits around the center. Yeah right. No galaxy really starts off that way. Galaxies are in clusters and being acted on by one another. Many galaxies have satellites that perturb them and they were formed from smaller lumps that have gotten cannibalized. They’re dynamic places, so if we introduce some perturbations to the system, we can ask what happens then.

No need to really do this for the whole galaxy at this point. We can just look at the case of what would happen to any single star. It ends up that if you knocked a star out of its ideal orbit, the combined forces of the rest of the galaxy would work to try to restore its ideal position. But as with most restorative forces, it will tend to overshoot. Thus, you get harmonic motion. Not only do you get this towards and away from the center of the galaxy though, you also get it in the direction of motion. The combination of these two motions means that the star would make little orbits about its idealized location. The Sun does this too. Its motion in relation to the idealized point it should be (known as the Local Standard of Rest or LSR) is known as “Peculiar Motion”.

So let’s try to picture what that looks like. In this image, I’ve drawn the idealized LSR for our star in green. On top of that, I’ve sketched the path it would travel around an idealized point in red at four different points in the full orbit. The extent of this is grossly exaggerated of course, but it will illustrate the point.

Now let’s have the star make an integer number of rotations around its small circle every time it goes around the full big circle. If we take the star to be at its furthest from the center of the galaxy at point a, then it would be at its closest at b, furthest again at c, and closest again at d. Now putting the overall true motion of the star (in blue) in with the smaller wobbles, the true motion becomes apparent: Stars have elliptical orbits.

What’s more, the way these elliptical orbits line up isn’t the same at all distances from the center of the galaxy. Rather, the orientation of the major axis of the ellipse will rotate as you move out. That means that if we drew is successive ovals, each one would be slightly skewed resulting in a pattern like the one I’ve shown here.

The result of these skewed orbits is that at some points around the galaxy, stars tend to all bunch up more than at other places. And what happens when you get a bunch of massive things bunching up? It creates a gravitational potential. The result is that stars will speed up as they fall in making a lack of stars on the trailing edge but then be slowed down again as they exit, creating a pile up on the front edge. If spiral arms really were some magical place that could get wound up, we shouldn’t expect to see this. But we do, which suggests that the Creationist version of spiral arms doesn’t fit reality.

And this is what a spiral arm is. It’s the crowding together of a bunch of stuff as its slowed down exiting the potential well caused by the spiral wave. And it turns out these things are very stable. So the Creationist claim that they must be very young because galaxies should “wind up” is just wrong. It’s using a horribly outdated idea of what spiral structure is. Not that this is surprising.

But how robust is this explanation? Turns out it does very well to explain not just the very nice two armed spirals like M51, but it also can explain the not so neat spiral galaxies like M101. It just takes a different number of orbits around the small path per full orbit. And even the flocculent spirals with patchy arms can be explained through this, using non-integer numbers of rotations or linear combinations of many states.

I hope that clears up what’s really going on with spiral structure. If you’re really interested in seeing the math behind this, it should be in most junior/senior level astronomy texts.

Sunday, June 08, 2008

What is death? Death is when something with life dies. Does that mean plant death? No. God tells us in Leviticus and many other places that life is in the blood of the creature. "For as for the life of all flesh, its blood is identified with its life."

And you've got to appreciate how amazingly inept these people are at logic. Take out the nonsensical qualification in the last sentence and you get, "death is when someone or something ... dies."

What an amazingly profound and useful definition. Really, does that qualify as circular reasoning? It doesn't even go in a circle. It just sits in one spot. This is supposed to be "upper-level science with the most in-depth, insightful science curriculum"?

Friday, June 06, 2008

I've been too lazy too cook recently, so I've been eating more fast food than is probably good for me. I've been getting a lot of fries, but I suppose I forgot to order the Pareidolia Extra Stupid Meal. Apparently, two fries at a right angle = Jeebus on teh cross.

I think my favorite part of that video is the old lady saying, "In my 88 years, I've never seen anything like this."

Really? You've never seen two objects at (roughly) right angles to one another? I think you need to update that prescription grandma. It seems to have expired.

Monday, June 02, 2008

Teacher: And that students, is how you successfully tie a square knot when you go rappelling.

Student raises hand.

Teacher: Yes Timmy?

Timmy: I've also heard my friends talking about using the double fisherman's knot or the European death knot. Are those good knots?

Teacher: I'm sorry Timmy. I'm not allowed to discuss that.

Timmy: But if other knots are better, shouldn't we know about them too? I mean, we're probably going to go climbing anyway so isn't having more knowledge beneficial?

Teacher: Too much knowledge is dangerous Timmy. Your parents are worried that you might use all this practical knot tying knowledge to tie up complete strangers and hold them hostage! Besides, those knots aren't part of the curriculum.

Timmy: But I'm asking the question.

Teacher: It doesn't matter. Your parents don't want you knowing it, so even if it could save your life, I'm not going to teach it to you. Otherwise I could lose my job.

Timmy: But isn't your job to teach us?

Teacher: I'm only supposed to teach you what your parents want you to know on this subject. They're very touchy about it.

Timmy: But my parents can't even tie their shoes...

Hahahaha! Silly story isn't it? Evil parents wanting to keep their kids ignorant about knots that could save their life if they're going to engage in the risky sport of rappelling. It's completely impossible that a bunch of freedom loving people that are all about academic freedom would ever censor information and try to pass bills ensuring that any teacher that (God forbid) answered questions on a topic be subject to severe penalties...

But of course, if there's not enough dust on the moon, then there's probably not enough dust on Mars. And with the new Phoenix lander on the surface digging through that dust, I'm willing to bet it's not going to be long before we start hearing "Mars dust" arguments popping up. And I bet they're also going to point to this press release showing that the dust is really thin. Thin enough that the retrorockets that helped give the lander a soft landing was able to blow it away to uncover a solid substrate.

Thursday, May 15, 2008

All my finals are finished and I'm just working on doing my term paper for my nanotechnology course. I'm a gigantic procrastinator, so I haven't even chosen a topic until the day before it's due (not a problem since it's only a 4 page paper). In skimming possible topics though, I found this journal article which uses nanotubes to detect the presence of chemicals in chili and hot sauces, providing an accurate measure of just how spicy that food is.

Thursday, May 08, 2008

Last time, I walked through the basic idea of photometry leaving off with the ever so epic cliffhanger that things are always harder than they seem at first. Nature may be able to be broken down into a series of simple principles, but the combining of those principles always serves to make life hard for us science types. We try to find ways to minimize some of those confounding tricks nature plays by making simplifying approximations, but we can't always get rid of them. And this is no less true in photometry.

So let's now take a look at what happens when we start putting a bit more reality into the discussion.

I'd said earlier, that stars behave like black bodies and showed a bunch of nice, pretty curves. That'd be a great way to do things if only there weren't that one little bit of the star that mucks the whole thing up: The atmosphere. Since it can absorb photons out of the nice, simple blackbody spectrum (forming the absorption spectra), we can't just ignore them and toss our photometric filters wherever we'd like. If we did, we might end up tossing one right over the calcium K line which would cut out a ton of the light we'd receive and make whatever filter we slapped over that wavelength give fainter readings than it should. No good!

Instead, the position of filters and photometric system is carefully chosen to avoid such potential pitfalls. We have the spectra for thousands of stars, and we know where lines will typically be. Thus, we can select regions of the spectra where there isn't absorption (or emission) lines and you have primarily a continuous blackbody spectra.

Well, hopefully. Depending on the photometric system you choose, the bandpasses that they're standardized for can either be wide, intermediate, or narrow band. The Johnson/Cousins system is a wide band system. In fact, it's so wide, the filters actually have a bit of overlap. In such a case, lines are unavoidable, but since you're also picking up continuum on either side, they're (hopefully) swamped by signal.

For smaller bandpass systems, this is less of a problem... so long as those lines stay where we can keep track of them. But they don't always do that. If the object we're looking at is moving towards or away from us, the entire spectrum can get shifted one way or the other. That's great if you're trying to do radial velocity measurements, but if it shifts a spectral line into one of your filters, it could be trouble! If that's the case, you'd probably have to use some other filter system to avoid the lines.

But this all assumes that you can avoid the lines. In hot stars, it's not too hard. Nearly all elements in such really hot stars are completely ionized so you don't have any electrons in the orbitals. As such, you don't tend to have very many absorption lines. However, the cooler the star, the more electrons fall into orbitals to do the absorbing and the more lines you get. If you start getting to really cool stars, it's not just atoms you have to worry about, but molecules which can absorb even more because they can store energy in vibrational and rotational states too. Thus, in the spectra of a cool star, lines are everywhere! No chance of avoiding them there. Thus, errors are much larger in cool stars than in hot ones.

And line problems don't end there! If you do have a star that has absorption lines, remember that that's taking out light from the spectrum. Since that light has energy, and energy must be conserved, that energy is going to manifest itself somewhere else. Since you can't get more energy out than you've put in with the absorption lines, that means that the bluer lines that are taken out (blue light is shorter wavelength and higher energy) will get broken down into more, longer wavelength (and lower energy) photons that will get remitted at a wavelength that's not absorbed. Thus, when you have something being absorbed, it can pop back out at longer wavelengths enhancing the signal in that part of the spectrum. Typically, this isn't a big problem for a few lines, but if you have a whole bunch of closely spaced lines (like you do in cooler stars) a line blanketing effect kicks in and it can cause some problems.

However, there can be times when you actually want to stick your filter right into an absorption feature. And example of this would be the atmospheric activity value that I keep seeing the research I've been working on. The idea behind it is that stars like the Sun have whopping great lines due to absorption from calcium (the H & K lines in the visible part of the spectrum). But for active stars, there's actually a tiny emission peak at the center of this great whopping dip. Thus, if you can measure that emission peak in relation to the depth of the absorption line, you can get a handle on the atmospheric activity. Thus, you can toss a nice intermediate band filter on the H or K line, and a narrow band filter on the emission bit and again, without having to go through all the time and trouble of getting complete spectra, you've got the information you need.

So it's not always bad, but there's still other challenges.

The next major one is that light, as it passes through our atmosphere and optics, ends up getting smeared out. Instead of stars being perfect, infinitely small points that only fill a single pixel on our cameras, the signal gets spread out. If we look at the brightness as a function of distance from the center of a star on our CCD, we'll get something that looks like the image to the right. In the center, the image is the brightest, but some of the light is smeared off in every direction, making it get dimmer and dimmer as you move from that central point. However, since that trail that's dropping off is still some of your precious photons, you can't just ignore them! You have to worry about that too.

This isn't really all that hard though. To see why, let's look at that same star plotted slightly differently. Instead of being a 2-D plot, this one is of the same star's intensity profile plotted in 3-D. The grid represents the grid of CCD pixels and the height above the plane is how bright the star looked on that pixel. We can see it's the same sort of thing that happened in the 2-D image; It's brightest at the top and trails off. But we can still deal with that because at some point, it's dropped off enough that you don't really lose much by just chopping it off and counting up what you have. Essentially, the star looks like a big hill and if you chop the hill off at the bottom and count up all the dirt in it, you can still do just as well as if all that dirt was in a thin narrow column. Crisis solved!

At least, until another star comes along. The method I just described (aperture photometry) works great for fields of stars in which the stars are relatively isolated. However, if you have two stars that are close enough together that the hill of one blends into the hill of another, then you can't just chop it off at that certain radius because you'll be getting dirt (light) from the other hill. And you can't ignore it in the parts where it overlaps because that's your signal! For just random sections of the sky, this isn't typically a problem, but in high density regions like the plane of the milky way and clusters, it becomes a huge problem.

Time for another trick. And this one's really sneaky. The idea is, since we're looking at a moderately small part of the sky, any atmospheric perturbations that are inflicted upon our field will be more or less the same. Since the light is going through the same optics, that should be the same too. Thus, the amount of distortion should be the same for all stars. What that means in more useful terms is that the shape of each hill should be the same. They should all be described by the same (Gaussian) profile. The only thing that's different is how tall or short the hill is. But the rate that the hill falls off is identical for every star.

So if we can figure out what that shape is, we can make a model hill that we just slide up and down for brightness. To find the shape (known as the point spread function) of the hill, you first need to find some isolated stars whose hills aren't being polluted by other nearby stars. The more stars like this you can build your model off of, the better the model, and the better the data. This method is called "Profile Fit" or "Point Spread Function" (PSF) Photometry. It's not too bad since computer algorithms will try to pick out those isolated stars. Unfortunately, they're not that great and you have to go through each one manually to confirm it's really isolated (and not on the edge of the CCD or anything). When I was doing this for my San Diego internship, the computer would find about 200-250 candidate stars. For each image. For each filter. It took two solid weeks of work to get good modeling stars. It's laborious (which is why the task is relegated to undergrads and data monkeys), but it's doable.

So there's some of the problems that astronomers face doing photometry and how they can sometimes be overcome. This is pretty much all there is to understand how photometry works and we do what we do. About the only thing I haven't gotten into very much is a more detailed explanation on just what else we can get out of various filter systems. There's more than just the temperature (for example, the DDO photometry system can give an indication of iron abundance), but that discussion requires delving into each photometric system independently and I'll save it for another post.

In one of my earlier posts I discussed the information that can be gleaned from the HR diagram, but what I didn't really discuss is how such diagrams are really constructed. I mentioned that it's necessary to either pick stars that you know the distance to (so you can correct for dimming due to distance) or stars in a cluster that are all at the same distance (so there is no variation).

But what I didn't mention is precisely how astronomers go about getting the information for the brightness and the temperature. If you've read my post on the HR diagram, I've mentioned one way: You find the peak emission and use Wien's Law to get the temperature.

But doing that requires getting the spectra of the star. And therein lies the problem. To get the spectra of a star, you have to pass it through a prism (or a diffraction grating as is more typically the case). But this means that instead of having a single dot on your image plane, you're going to have a band. And if you have lots of stars, you'll have lots of bands. And if you have lots of bands, they'll overlap and make a mess. So spectroscopy is slow because you have to do one star at a time. There's been some ways to get around this by using fiber optic cables at the image plane to intercept the light and send it to lots of different spectrographs, but such things have to be individually set up for every field you want to look at. What a pain!

And that's not the only thing that makes spectroscopy slow. Since you're spreading out the light that you're getting, this also means that the amount of photons hitting at any one point will be less. Your image gets fainter the more you spread it out into the rainbow!

So there's two major things that make doing spectroscopy slow work. It's good and necessary for getting things like the chemical composition, but if we really just want to make an HR diagram, isn't there a quicker way?

YES!

And that method is known as photometry. The trick of this is that instead of looking at all the wavelengths, it picks out just a few important ones and does the work that way.

The reason this works is that stars tend to behave pretty close to what's known as a "blackbody". What this means is that it gives off radiation in a certain way with a peak wavelength dependent on it's temperature. They're described by Planck's Law (setting the first derivative equal to zero and doing a few substitutions gives Wein's Law). But what's really important is that the wavelength or the color of the peak is determined by the temperature. It's easiest to explain with a diagram:

As you can see, the hotter stars peak off in the blue region, and have a greater luminosity. The cooler a star gets, the more red it's peak emission and the less energy it gives off (which is shown by the area under the curve or the first integral of the blackbody equation).

Like I've already said, through spectroscopy, you can get that entire blackbody curve (with the superimposed absorption and emission features). That's great, aside from the slow part. But how does only looking at a few specific points on that curve tell you what you need to know?

This is most easily demonstrated by example, so I'll just jump right in with the most common photometric system, the Johnson/Cousin system. This system has five filters:

U: Ultraviolet
B: Blue
V: Visual (green-yellow)
R: Red
I: Infrared

Each of these filters only allows light from a narrow range of wavelengths (known as a bandpass) to get to the detector. It's essentially looking at a series of five points along those blackbody curves I just showed.

So let's take that first blackbody curve, the one for a hot star, and put the filters on it (note: For some reason I didn't show the R filter. Also, the units are removed since for the purposes of illustration, all we need is a qualitative effect).

In this image, we can see that the filter doesn't intersect at equal luminosities. In the U filter, it's pretty low. It gets higher in B (which it should since we already said, it's a hot star), and then gets lower in the V, and is lower still in the I.

Now consider what happens if you take the difference between the luminosities of two filters. Most commonly done is the B-V so we'll use that for the example. If you do this, the B is greater than the V, so if you subtract it, you'll get a positive number. But remember, this is in luminosity and astronomers work in the magnitude system in which brighter stars are smaller numbers. It's backwards. So when talking in terms of magnitudes, a blue star will have a negative B-V.

So let's now look at a cool star on the same filters:

Here, if we try the same thing, and take the B-V luminosities, the star is brighter in the V than it is in B, so if you're talking about luminosity and take B-V, you'll get a negative number. Flip that around for magnitudes, and you get a positive number.

So already, you should be able to see the trend. In terms of magnitudes, a negative B-V means a hot star. A positive B-V means a cooler star. The more negative you get, the hotter it gets. The more positive you get, the cooler it gets.

This is great! It fixes both problems we had earlier. It doesn't spread the starlight out, so images don't take any longer to expose. Nor does it require you to put each star through a slit. You can do an entire field of stars at once! And this is, for the most part, exactly what I did for my research 2 summers ago. Using this basic principle, I worked out the H-R diagram for NGC 7142 (except that when we use photometry to replace the temperature, we call it a "color-magnitude diagram" or CMD). Of course, there were a few nuances that made it a bit more difficult than what I've just described.

But instead of going into all that now, I'll save that for another post.

So what's the point of posting these things all the time? Is it to show how stupid people can be?

Not really. Trying to find patterns in things is part of our genetic programming. I'm certainly not going to fault anyone for doing it. However, what I can fault them for, is taking it far too seriously. The reason is, that it demonstrates a gigantic case of confirmation bias. Odd shapes turning into miracles only works when you've already had the image implanted in your mind.

This image (I'm linking to it because it's possibly NSFW depending on how you look at it) illustrates it perfectly.

If you haven't seen the image, don't scroll down anymore till you have unless you want to spoil the surprise.

I bet most of the people reading this blog saw the same thing I saw: A naked couple embracing. However, when the same image is shown to people that wouldn't have already been made aware of such things (ie, children) the image is of 12 dolphins (they're in the dark regions).

Brother Jed and his companions made a trip to the University of Kansas today. At one point, we managed to get his older, portly companion on the topic of the age of the Earth. I was there with a grad student in Geology. It quickly became apparent, that despite Jed's companions claims to formal training in Geology are grossly exaggerated and he presented either gross ignorance or outright lies.

For example, one of the claims this person made is that uplift due to plate tectonics has never been observed. This was directly refuted by the Geology student with numerous examples and a quick Google search returns just such measurements from Papua New Guinea's Finisterre mountains.

He also claimed that convection zones in the Earth which drive tectonic activity must be square. A thorough search for this information returned no results. Searching scientific journals returned no results. Even a check against common sense shows how silly this claim is. Just try drawing a square (not rectangle) inside a circle. It requires that the material MAGICALLY change direction with no forces acting on it far from the core. Talk about miracles!

This person also attempted to invoke polystrate fossils (ie, trees cutting through many layers of deposited sediment) as indicative of a young Earth. What he neglected to mention was that these fossils are only found in places where you should expect frequent deposition rates (ie, near rivers or regions of volcanic activity). When actually dated, radiological dating confirms this prediction. Rather, Jed's companion hypocritically dismissed this, after having just previously argued against uniformitarianism.

Many of the other arguments he presented are so poor, that the major Young-Earth Creationist organization, Answers in Genesis, suggests they not be used. Among them that Jed's companion invoked:- Plate tectonics is fallacious.- There are no transitional forms- Paluxy tracks prove that humans and dinosaurs co-existed.- Moon-dust thickness proves a young moon.

If many of this person's BEST arguments are refuted by even Creationist organizations and simply searching Google, I hate to think what this says of his intellectual honesty and scholarship concerning his other arguments. Nor is his character much better. When presented with contradictory evidence, this person did not provide a rebuttal, but instead chose to reply by calling us "Morons!" I was personally called a "moron" five times.

I never caught this person's name, whoever this Santa Claus look alike, fisher hat wearing jerk was, he's an embarrassment to an already embarrassing ministry. I seem to recall St. Thomas Aquinas having something to say on how disgraceful it is for Christians to show ignorance in science due to it suggesting that they are ignorant to truth in general. Perhaps Jed's companion should learn from him.

Yesterday was the National Day of Prayer for the silly minded people of the nation. Meanwhile, I made my annual trip to the blood bank and made a real donation.

And what have all the silly minded people been up to? Well PZ has more, but I find the irony of the one that got dressed up in a sack and ashes to pray getting caught making illegal financial transactions especially amusing. Oops.

Tuesday, April 29, 2008

For those that haven't followed this blog for a long time, one of the things you may very well have missed is that back when I started, I had a series of posts about the basics of how astronomy learns what it does. It started off with a look at where the light we look at comes from, and then discussed the difficulties it has getting to us, how we detect it, and finally, how we learn things from it. I stopped added to it back in the summer of 2006 because I didn't feel there was much more to add on that really fundamental level, but I noticed today when I was planning to write up something about my current research that there are a few topics that I never explained so I intend to do a bit more on that series.

But for those that haven't seen it before, here's the list of posts in my Intro To Astronomy series. I'll keep this updated and put a link in the side bar to act as a standard reference.

Tuesday, April 22, 2008

Yeah, yeah. I know God is Not Great (Christoper Hitchens) wasn't the next book on my reading list but I found an audiobook of it cheap and it's a lot easier to listen to something walking to campus and back than it is to read (unless I want to wander into oncoming traffic).

So listening to an audiobook was new to me. It's a very different experience and I'm not all together sure how much it affects the perception of I have of the book, so I'll pretend it didn't in any large way.

Anyway, contrary to what you'll probably expect, I ended up finding God is Not Great to be a pretty worthless book. Perhaps it was the experience of listening to an audiobook, but I didn't find a single passage that was noteworthy enough to quote (which if you've paid attention to my other reviews is a startling exception).

The book started off well enough. It introduced the danger religion poses: Encouraging people to do downright stupid things due to a lack of critical thought under the guise of "faith". And worse, the disasters it causes are supposed to be tolerated. The best example given was a Jew performing circumcisions followed the instructions given in the Torah which calls for the foreskin to be bitten off. In the process of doing this, the practitioner passed along herpes to the children he was circumcising. One died and another suffered brain damage. Was this in a backwater village? No. Modern day New York. And instead of protesting this act, the mayor called for it to be respected. Another of the early chapters looked at how some religious beliefs are just plain stupid. Namely, this chapter focused on the demonization of the pig of some religions.

Salman Rushdie's plight was another major point that Hitchens made that was particularly good. Rushdie, whose fiction novel, The Satanic Verses sparked outrage in the Muslim community has had death threats and even attempted assassinations leveled at him due to a fatwa issued. As with the herpes transmission before, instead of condemning this, many instead blamed the victim thinking the order to murder over a work of fiction as something that was somehow inherently worthy of respect because it was religious.

The argument against the nonsense that religion makes people behave better was addressed very well, showing that many of the figureheads of the better behaving religious weren't really all that great. For example, Ghandi may have been kindly, but tried to (and in some manners succeeded to) drag a country down into a new dark age after secular powers had worked to gain independence.

In anticipation of the reverse of that argument, Hitchens attempts to address the other side of that coin: Atheism makes bad people (a particular favorite of the trolls here), pointing the finger squarely at Stalin, Pot Pol and Lenin. Hitchens' response was not at all convincing. The short version is that those that are often pointed to have little to do with what we typically consider atheists, meaning people who stick to a material philosophy and rule out the supernatural. Rather, they built themselves and their empires into their own gods, supplanting religious ideas with nonsense like Lysenkoism. As such, they had more in common with the religious counterparts than typical atheists. What Hitchens manages to miss however, is the more fundamental point: None of them every claimed to undertake their programs because of their atheism. Thus, trying to point to that as a cause is as rational as pointing to the fact that they were all white men. The same can not be said for their religious counterparts. So it seemed to me that Hitchens fumbled a strong argument there.

But aside from these few highlight, the book took a serious turn for the worse. The supporting arguments tended more towards personal testimonies which were rather ineffective and not suited for the grand generalizations Hitchens often drew from them. The main argument of chapters often became hopelessly lost in the rambling narratives Hitchens digressed into. The argument that the "miracles" espoused by religion is the equivalent of parlor tricks when compared to that which science has brought forth was cute, but not especially convincing.

Overall, out of 19 chapters, only five or six were particularly interesting and even then, only in parts. After "reading" this book, it seems strange that theists should get so upset about it given that it's not even that good.

Tuesday, April 15, 2008

The development of telescope technology has been a long process. In recent years, most large single mirrors for telescopes have been based on the traditional design of a glass base, shaped into a concave parabola, coated with a reflecting surface (typically aluminum) deposited in a evacuated vaporization chamber. The parabolic shape is often obtained by beginning with a liquid glass which is placed into a mold and spun as the glass is allowed to cool. The balance of the centrifugal and gravitational forces creates a parabola, the depth of which (and hence the focal length of the telescope) can be controlled through the rotation speed.

The major disadvantage to this design is that the glass mirror becomes excessively heavy and is unable to support its own weight well above a radius of eight to ten meters. As such, new techniques have been developed that use segmented mirrors. Another novel technique that is currently beginning to see use is that of using liquid mirrors that do not solidify. This practice has already been put into use with the Large Zenith Telescope which boasts a 6m diameter liquid mercury mirror.

Unfortunately, mercury and most other highly reflective liquids are prohibitive due to their toxic and/or unstable natures. Additionally, with the current drive to establish new locations for possible observatories, such mirrors would be required to function in new environments. One of these proposed environments would be a possible moon base. In such a case, traditional glass mirrors would be impossible, due to the high cost of transportation. Thus, a liquid mirror becomes much more practical, if an appropriate liquid can be found.

The requirements for such a moon based mirror would be that they have extremely low freezing temperatures and retain their liquid state in vacuum as well as be non-toxic and stable. Although a number of possible candidates exist, few have an intrinsically reflective nature, although Burns (2008) reports that Lithium Ammonia may be suitable. This requires that such a material be coated with a reflective surface.

Finding suitable materials that fit these criteria and attempting to coat them was the subject of a 2007 Nature paper by Borra et al. In addition to the restrictions placed on a possible telescope by the inhospitable lunar conditions, the coating process also adds additional constraints in that the coating must be smooth enough, and reflective enough to serve as a functional mirror in the desired wavelength range (infrared in this case).

Since coating of liquid surfaces had not yet been attempted, the researchers attempted to coat several different materials using a vaporization deposition resulting in films only a few nm thick. Most of these attempted coatings were unsuccessful. From this, they further refined their liquid criteria to require the liquid to have nearly zero vapor pressure and high viscosity. The ideal class of compounds they determined to be ionic liquids which are salts in liquid form at low temperatures (defined as below 373 K). The challenge was then to apply a silver coating in order to make a suitably reflective surface.

Fig 1. - Reflectivity curves for various silver coated liquids. PEG curve is shown for an attempted liquid deemed not suitable and not discussed in this post. As discussed in the paper, the most promising is the ionic liquid with an initial chromium layer (5nm) followed by a 30nm silver coating. Curves only extend to 2.2 μm due to instrumentation limitations. (Borra 2007) .

To do this, Borra et al. applied a thin film of silver nanoparticles to the surface with diameters of only a few tens of nanometers. However, the nanoparticles tended to diffuse into the liquid substrate forming a colloid, reducing reflectivity with respect to metallic silver. In order to mitigate this problem, the group first applied a chromium layer. This layer tended to bond easier and form a better surface to which the silver could then be applied. With this additional coating, Borra et al. were able to increase the reflectivity as shown in Figure 1.

Although reflectivity is as high as 80% for some wavelengths, Borra notes that this is still low for standard astronomical mirrors which often have reflectivity over 95%. In an earlier paper (Borra, 2004), it was noted that these surfaces would often begin with a higher reflectivity, which would decrease over the course of a week by ~8% and remain relatively constant thereafter. They surmise that greater stability and reflectivity may be reached with different metallic nano-coatings. Borra did not note whether or not the chromium backed silver coating had the same degradation as previously mentioned.

Aside from just being able to reflect incoming light, mirrors would also be required to have a suitably smooth surface that they would produce high quality images. To analyze this, the group mapped the topographical distribution via electron microscopy, of the produced surface (with a 5nm chromium layer and a 30 nm silver coating) and found it had a peak to valley depth of 0.0373 µm which gives an excellent optical surface (see Figure 2).

In the 2004 paper, Borra also describes the possibility that mirrors could be further shaped with the application of magnetic fields, if the mirror’s substrate was composed for ferromagnetic liquid. Although it would not be necessary in the lunar vacuum, controlled deformations have been used on telescopes to correct for atmospheric aberrations. This technique is known as adaptive optics.

However, the liquid mirror technique is not entirely without drawbacks. One of the most obvious is that the mirror must remain horizontal. Tilting the mirror’s axis would cause deformation in the topography, rendering the surface unusable for observations. In other words, the mirror must be permanently fixed on the observer’s zenith. However, telescopes such as the famous Arecibo, are also zenith based and function quite well for their particular sorts of observations. Namely, this liquid mirror telescope would be quite well suited for deep field imaging since, at large distances, a greater volume of space is shown. But to do imaging of such distant objects, exposures must be taken for a longer time. Since the telescope would be turning with the moon, this would limit the total exposure time as the object swept over the field of view. As such, several images would have to be taken and subsequently added to produce a suitably deep image. Again, on the moon, this would be less of a problem since the moon has a slow rotation rate (~28 days), allowing objects to stay in the field of view for longer times.

Although not discussed, another problem I could foresee would be a possible interruption of power. If power to the rotator would be lost, the centrifugal force would vanish, and the liquid substrate would settle back into a flattened shape. Most likely, this would result in a tearing of the nano-coating, causing the mirror to need to be entirely recoated. If the liquid were viscous enough, short power interruptions may be mitigated. Regardless, this may not be as large of a problem as it may otherwise seem, since telescope mirrors are frequently resurfaced as it is, in order to retain a fresh and dust-free surface.

Overall, the work of Borra et al. has clearly shown that there is a great deal of promise in the formation of mirrors using nano-coated ionic liquids. Even in these initial tests, they have been able to achieve surfaces which are smooth enough to make excellent surfaces. Although the surfaces are not yet reflective enough to meet the standards for astronomical instrumentation, it is likely that with further experimentation with different coatings as well as additional intermediate substrates, it is likely that this can be greatly improved. Yet while the concept has been well established, the question remains whether or not this is the most economic or feasible option for a liquid mirror. As Burns suggest, it is likely that there exist other materials that have similarly high reflectivity and would not suffer from the drawback of requiring an additional coating. For example, the liquid lithium ammonia mirror they recommend has reflectivity curves similar in quality to that of these more complicated, coated mirrors of Borra (see Figure 3).

As such, although the concept is sound, it would seem that further development and testing will be necessary before it can be determined which sort of mirror would be best for use in a lunar environment.Borra, E.F., Seddiki, O., Angel, R., Eisenstein, D., Hickson, P., Seddon, K.R., Worden, S.P. (2007). Deposition of metal films on an ionic liquid as a basis for a lunar telescope. Nature, 447(7147), 979-981. DOI: 10.1038/nature05909